New Industrial Process of PTMG Catalyzed by Solid Acid Supported on Mesoporous Material

Polymerization of tetrahydrofuran (THF) catalyzed by solid acid in the presence of acetic anhydride was studied. Moderate Lewis acid catalyst produces PTME (PTMG-diacetate) having appropriate molecular number (Mn). Mixed oxide materials show good performance. Mass transfer study suggests the importance of pore size of the support and of the location of active sites. They affect the M_n and the polydispersity (M_w/M_n) strikingly. The commercial technology has established by utilizing these results.     

MALDI-TOF and MALDI-FTICR imaging mass spectrometry of methamphetamine incorporated into hair

A new approach is described for imaging mass spectrometry (IMS) of methamphetamine (MA) incorporated into human hair using matrix-assisted laser desorption/ionization (MALDI)-time-of-flight (TOF) and MALDI-Fourier transform ion cyclotron resonance (FTICR). A longitudinal section of a lengthwise manually-cut single human hair shaft from a chronic MA user was directly analyzed by MALDI-TOF-IMS after deposited with α-Cyano-4-hydroxycinnamic acid matrix. A barcode-like image, which was most probably generated with repeated intakes of MA, was for the first time obtained by monitoring MA-specific product ion in the selected reaction monitoring mode. Laser beam scan lengthwise-cut hair shafts gave only poor mass spectra of MA, probably due to the loss of MA and/or the thermal denaturation of hair. The identity of MA detected in hair was further confirmed by MALDI-FTICR mass spectrometry. A combination with ultra-high resolution mass spectrometry by FTICR provided indisputable identification of MA. The MALDI-FTICR-IMS of another hair shaft from the same MA user also provided a barcode-like image by monitoring the protonated molecule of MA with ultra-high resolution. The two barcode-like images exhibited a close resemblance. Thus, MALDI-IMS can offer a new perspective: 'imaging hair analyses for drugs'.     

Cell-Encapsulating Hydrogel Puzzle: Polyrotaxane-Based Self-Healing Hydrogels

Slide-ring hydrogels using polyrotaxanes have been developed as highly tough soft materials. However, they have never been used as biomaterials because of the lack of biocompatibility. Meanwhile, self-healing hydrogels are expected to improve fatigue resistance and extend the period of use. However, owing to the lack of high mechanical strength, they are limited in their use as biomaterials. Here we first developed a biocompatible self-healing/slide-ring hydrogel using glycol chitosan and a water-soluble polyrotaxane. We obtained excellent mechanical toughness and biocompatibility to promote the proliferation of human umbilical vein endothelial cells (HUVECs) encapsulated in the hydrogel. Owing to the rapid self-healing property, the cell-encapsulating gels adjusted arbitrarily, maintaining good cell proliferation function. Therefore, slide-ring hydrogels enable the use of biomaterials for soft-tissue engineering.     

Crystal structure and lattice vibration of proton dissolved BaZr0.8Sc0.2O2.9

Heat capacity and neutron diffraction measurements were carried out to determine the location of protons in the crystal of proton conducting perovskite oxide BaZr_0.8Sc_0.2O_2.9. The heat capacity of proton- and deuteron-dissolved BaZr_0.8Sc_0.2O_2.9 showed a slight difference from that of the dry sample. It indicates that the librational motion of the OH(OD) group is not excited below room temperature. The neutron diffraction experiments on the deutron dissolved sample indicate that the deuteron exists near the 12h site.     

Stereoselectivity of superacid-catalyzed Pictet-Spengler cyclization reactions

[reaction: see text] High stereoselectivities were found in a wide range of superacid-catalyzed Pictet-Spengler cyclization reactions. Particularly in the cases of 2-alkyl-N-benzylidene-2-phenethylamines, an enhanced stereoselectivity was observed under the superacid conditions as compared with the corresponding weak acid (TFA)-catalyzed (monocationic) cyclization reaction of the N-benzylidene-2-(3',4'-dimethoxy)phenethylamines that bear electron-donating groups on the cyclizing aromatic ring. The computational study also supported the energetic favorability of the cyclization of the N,N-diprotonated imine and revealed a significantly early transition-state structure.     

Spin crossover phenomenon accompanying order-disorder phase transition in the ligand of [FeII(DAPP)(abpt)](ClO4)2 compound (DAPP = bis(3-aminopropyl)(2-pyridylmethyl)amine, abpt = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole) and its successive self-grinding effect

The spin crossover phenomenon of the recently described spin crossover complex [FeII(DAPP)(abpt)](ClO4)2 [DAPP = bis(3-aminopropyl)(2-pyridylmethyl)amine, abpt = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole] accompanying an order-disorder phase transition of the ligand was investigated by adiabatic heat capacity calorimetry, far-IR, IR, and Raman spectroscopies, and normal vibrational mode calculation. A large heat capacity peak due to the spin crossover transition was observed at T(trs) = 185.61 K. The transition enthalpy and entropy amounted to Delta(trs)H = 15.44 kJ mol-1 and Delta(trs)S = 83.74 J K-1 mol-1, respectively. The transition entropy is larger than the expected value 60.66 J K-1 mol-1, which is contributed from the spin multiplicity (R ln 5; R: the gas constant), disordering of the carbon atom of the six-membered metallocycle in the DAPP ligand, and one of the two perchlorate anions (2R ln 2), and change of the normal vibrational modes between the high-spin (HS) and low-spin (LS) states (35.75 J K-1 mol-1). The remaining entropy would be ascribed to changes of the lattice vibrations and molecular librations between the HS and LS states. Furthermore, [Fe(DAPP)(abpt)](ClO4)2 crystals disintegrated and became smaller crystallites whenever they experienced the phase transition. This may be regarded as a successive self-grinding effect, evidenced by adiabatic calorimetry, DSC, magnetic susceptibility, and microscope observation. The relationship between the crystal size and the physical quantities is discussed.     

Self-assembled plasmid DNA network prepared through both triple-helix formation and streptavidin–biotin interaction

Plasmid DNA responds to external stimuli to change the degree of supercoiling. As a result of its unique topological change, plasmid DNA is considered to be a new functional material. In addition to its stimuli-responsiveness, plasmid DNA has the capability of forming a triple helix with a triple-helix-forming oligonucleotide (TFO). The triple helix is formed in aqueous conditions and arises through recognition of specific sequences, and may lead to the formation of supramolecular architectures. With this in mind, we analyze the self-assembly of recombinant plasmid DNA with two sequences for triple-helix formation and TFO by means of surface plasmon resonance. In addition, the network formed by self-assembly of the recombinant plasmid DNA with biotinated-TFO and streptavidin is prepared and evaluated by atomic force microscopy (AFM).

Schematic illustration of plasmid DNA network.     

Effect on bending behavior of counter cation species in perfluorinated sulfonate membrane–platinum composite

The perfluorinated sulfonate membrane (Nafion ®117)–platinum composites having H⁺, mono- and bivalent metal ions as counter cations in the membranes were prepared and the bending behaviors of the composites actuated by the step voltage were investigated in deionized water. The bending behaviors of all composites have the same tendency as the composites to bend quickly to the anode side just after applying the step voltage and gradually to bend back to the cathode side in spite of keeping on the application. However, they show differences in the bending rate and the maximum displacement to the anode side just after applying the step voltage, which are influenced by counter cation species in the membrane. In particular, the composite having Li⁺ has the largest maximum displacement (about 1.1 mm) to the anode side. The relationship between the maximum displacements of the composites and water states in the membranes were studied. The maximum displacements of the composites depend on the water content in the membranes. In both series of the composites having mono- and bivalent metal ions, the maximum displacements increase with increasing water content, except the composites having Rb⁺ and Sr²⁺ which belong to fifth period in the periodic table. In spite of the result that the water content in the membrane having H⁺, which is about 20wt%, is nearly equal to that in the membrane having Na^a, the maximum displacement of the composite having H⁺ is only about one-third as large as that of the composite having Na⁺. The water structures in the membranes were investigated by using differential scanning calorimetry (DSC). The DSC endothermograms obtained indicate that the freezing water in the membrane having H⁺ has a much stronger interaction with sulfonate groups and counter cations than that in the membrane having Na⁺. It is concluded that the content and structure of the freezing water in the membrane have a profound effect on the bending behavior of the composite. © 1998 John Wiley & Sons, Ltd.     

Enzymatic Degradation of Semi‐IPN Hydrogels Based on N‐Isopropylacrylamide and Dextran at a Specific Temperature Range

The temperature‐dependent enzymatic degradation of semi‐IPN hydrogels consisting of dextran grafted with thermo‐responsive chains (lower cloud point) and a thermo‐responsive crosslinked matrix (higher cloud point) was examined. Enzymatic degradation of the semi‐IPN hydrogel was significantly inhibited below the lower and above the higher cloud point. Only between both cloud points, enzymatic degradation proceeded. The designed semi‐IPN hydrogel is therefore advantageous to achieve enzymatic degradation at a specific temperature range.